Historically, the meter readings that measure consumption of utility resources, such as water, gas, or electricity, have been accomplished manually by human meter readers at the customers' premises. The relatively recent advances in this area include collection of data by telephone lines, radio transmission, walk-by, or drive-by reading systems using radio communications between the meters and the meter reading devices. Although some of these methods require close physical proximity to the meters, they have become more desirable than the manual reading and recording of the consumption levels. Over the last few years, there has been a concerted effort to automate meter reading by installing fixed networks that allow data to flow from the meter to a host computer system without human intervention. These systems are referred to in the art as Automated Meter Reading (AMR) systems.
In an AMR system, an Encoder Receiver Transmitter (“ERT”) may be implemented within a utility meter in order to encode and transmit data utilizing radio-based communications. The ERT is a meter interface device attached to the meter, which either periodically transmits utility consumption data (“bubble-up” ERTs) or receives a “wake up” polling signal containing a request for their meter information from a collector (e.g., a fixed transceiver unit, a transceiver mounted in a passing vehicle, a handheld unit, etc.).
The ERTs typically communicate with a collector via wireless spread-spectrum modulation protocols, such as direct-sequence spread-spectrum (DSSS) and frequency-hopping spread-spectrum (FHSS). DSSS combines a data signal at the ERT with a higher data-rate bit sequence, sometimes called a “chipping code” or “processing gain.” A high processing gain increases the signal's resistance to interference. FHSS, on the other hand, operates by taking the data signal and modulating it with a carrier signal that hops from frequency to frequency as a function of time over a wide band of frequencies. With FHSS, the carrier frequency changes periodically, and therefore, potentially reduces interference since an interfering signal from a narrowband system will only affect the spread-spectrum signal if both are transmitting at the same frequency and at the same time.
In existing AMR systems, ERTs may be configured to accept and respond to commands. The enhanced services desired by customers and utility service providers will only continue to increase the need for performing these types of two-way communications. However, to minimize the consumption of power, ERTs are typically configured to only activate a receiver and listen for incoming messages when necessary. Accordingly, a remote device may not be able to transmit a message to the ERT while the receiver is deactivated. In this regard, existing automated meter reading protocols and related systems are limited in their ability to facilitate timely two-way communications with ERTs. In some instances, collectors used to collect meter readings are required to wait one or more intervals to issue a command or otherwise perform two-way communications with an ERT.